1. Field of the Invention
The present invention relates to a voltage level shifter, and more particularly, to a voltage level shifter formed by single-typed thin-film transistors.
2. Descriptions of the Related Art
Recently, thin-film transistor liquid crystal displays (TFT LCDs) are widely applied in personal computer monitors, televisions, cellular phones, digital cameras, and other electronic appliances. A TFT array is scanned according to a clock signal to activate pixels in turns. Since a high voltage level of the clock signal is required while the TFT array is scanned, the clock signal with a low voltage level has to be transferred to the high voltage level by a peripheral driving circuit, such as a voltage level shifter, and then provided to the TFT array.
FIG. 1 shows the circuit of one of conventional voltage level shifters, which comprises NMOS TFTs 101, 103, and PMOS TFTs 105, 107. Due to the coexistence of NMOS TFTs and PMOS TFTs, multiple doping MOS processes are generally necessary. This increases processing steps when integrating the voltage level shifter into a substrate of a TFT display, and manufacture cost increases.
One of the drawbacks of the conventional voltage level shifter is high manufacture cost. Therefore, it is desired in the industrial field that a voltage level shifter formed by single-typed TFTs to reduce manufacture cost.